Method for re-reaction of water phase in polyphenyl ether production
By treating the aqueous solution in polyphenylene ether production with extractants and alkali, the problem of its difficulty in recycling was solved, product quality and production efficiency were improved, and costs were reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANTONG XINGCHEN SYNTHETIC MATERIAL CO LTD
- Filing Date
- 2022-08-18
- Publication Date
- 2026-06-12
AI Technical Summary
The aqueous solution generated during the existing polyphenylene ether production process is difficult to recycle, leading to problems such as system blockage, frequent filter switching, unstable product performance, and high costs.
A mixture of aromatic hydrocarbons and imidazole ionic liquids was used to extract an aqueous solution, followed by alkali neutralization. The solution was then reacted with a chain extender and cuprous salt in a reactor to produce a high-quality polyphenylene ether product.
This enabled the effective recycling of the aqueous solution, improved the performance and yield of polyphenylene ether products, reduced production costs, and ensured the stable operation of the production system.
Smart Images
Figure CN117624585B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the production of polyphenylene ether, and more specifically to a method for aqueous phase re-reaction in the production of polyphenylene ether. Background Technology
[0002] Polyphenylene oxide (PPO) is one of the engineering plastics most imported by China. Its production process is long and the technology is complex. The synthesis of PPO mainly uses copper compounds and amine compounds as catalysts, and oxygen reacts with 2,6-dimethylphenol.
[0003] The production of polyphenylene oxide (PPE) generally requires the addition of an aqueous solution containing a complexing agent. The production process mainly includes polymerization, liquid-liquid separation, liquid-solid separation, drying, pneumatic conveying, and packaging. The aqueous solution produced during liquid-liquid separation is often treated as waste or simply disposed of in current production processes. However, this aqueous solution contains approximately 5-10% small-molecule oligomers and 1-2% amine solution. Failure to recycle it represents a waste of resources.
[0004] The existing process involves solutions containing oligomers entering a solvent recovery unit, then filtering them before entering a filtration and drying unit (in the finished product). The low amine recovery rate fails to meet reaction requirements, resulting in the following problems: 1. The solvent recovery unit filter frequently clogs, requiring frequent filter switching and disrupting normal production; 2. During filtration, the presence of alcohol solvents causes polyphenylene ether to form fine powder, leading to filter cloth clogging and incomplete washing (due to high washing pressure); 3. The high concentration of low molecular weight polyphenylene ether in the finished product results in poor tensile properties, impact strength, and other stability; 4. A large amount of amine solution containing protective chain extenders needs to be added after the low molecular weight oligomer solution enters the reaction, increasing costs.
[0005] CN113493565A discloses a method for preparing polyphenylene ether (PPE). After polymerization, a polymer is added to the product liquid to form a PPE solution. The solution undergoes phase separation to obtain an oil phase, which is then concentrated and precipitated to allow PPE to precipitate and yield the product. The method for treating the aqueous phase solution obtained during phase separation is not addressed. CN112940244A discloses a pretreatment method for PPE solvent recovery. This method involves reacting carbonates with the materials in the PPE solvent to be recovered to obtain basic copper carbonate and sodium 2,6-dimethylphenol precipitate. The precipitate is then filtered and washed, preventing blockage of pipelines and distillation columns. CN111217676A discloses a method for recovering solvents used in PPE synthesis; CN101423604A discloses a filtration system for PPE solvent recovery.
[0006] However, none of the above-mentioned existing technologies involve methods for treating and recovering aqueous solutions containing small amounts of oligomers and amines generated during the production of polyphenylene ether.
[0007] The recycling and reuse of aqueous solutions generated during the production of polyphenylene ether (PPE) can turn waste into treasure, be environmentally friendly, and reduce costs, which has important practical significance and value for PPE production enterprises. Summary of the Invention
[0008] To address the shortcomings of current technologies in polyphenylene oxide (PPO) production, such as the lack of recycling methods for the aqueous phase solution, difficulties in recycling, and operational instability caused by blockages, this invention proposes a method for the re-reaction of the aqueous phase in PPO production. This method involves extraction, mixing, separation, and re-reaction, effectively ensuring stable operation of the PPO production process, reusing previously waste materials, significantly improving the performance of the resulting PPO product, increasing reaction efficiency, reducing unplanned shutdowns and maintenance, and substantially lowering costs, thus achieving cleaner production.
[0009] The present invention achieves the above objectives through the following technical solutions:
[0010] A method for aqueous phase re-reaction in the production of polyphenylene ether includes the following steps:
[0011] (S1) Add the aqueous phase solution separated during the production process of polyphenylene ether to the alkaline solution through a metering pump and mix evenly.
[0012] (S2) The mixture obtained in step (S1) is pumped into the extractor, and at the same time, the extractant is added to the mixer and mixed evenly; the extractant is a mixture of aromatic hydrocarbons and imidazole ionic liquids;
[0013] (S3) The mixture obtained in step (S2) enters the cooling zone, is allowed to stand and separate into layers, the upper layer material goes to the reaction vessel, and the lower liquid phase is treated as wastewater.
[0014] (S4) Add chain extender, 2,6-dimethylphenol, and cuprous salt to the reactor, and pass oxygen-containing gas to carry out the reaction. After the reaction is completed, add chelating agent aqueous solution, cool, stand, and separate into layers. The upper layer is a polyphenylene ether solution. After post-treatment, the polyphenylene ether product is obtained.
[0015] Further, the aqueous solution separated during the polyphenylene ether (PPE) production process in step (S1) is obtained through liquid-liquid separation during PPE production. Specifically, it is obtained by reacting phenol derivatives (such as 2,6-dimethylphenol) and oxygen under the action of a catalyst (a complex of cuprous salt and organic amine), adding an aqueous solution of a chelating agent (such as ethylenediaminetetraacetic acid, ethylenetriacetic acid, diethylenetriaminepentaacetic acid, etc.), and then separating the solution through liquid-liquid separation. The aqueous solution contains 8-13 wt% PPE oligomer, 4-7 wt% mixed amines, 0.1-0.4 wt% cuprous salt, 0.2-0.6 wt% chelating agent, and may also contain 0.2-1 wt% aromatic compounds (mainly solvents such as benzene, toluene, and ethylbenzene). The role of the chelating agent is to cause the cuprous salt of the catalyst to lose its catalytic effect after chelation. If no chelating agent is added, the polymer will undergo side reactions under the action of the catalyst to produce phenolic quinone byproducts, which will adversely affect the performance of the PPE product. However, conventional methods are insufficient to remove this chelating agent, making direct reuse of this aqueous solution in subsequent production technically challenging. When using extractants, this chelating agent is typically extracted along with the polyphenylene ether oligomer. This invention first neutralizes this chelating agent into a salt using an alkaline solution, then extracts it with an extractant, ensuring that the majority of the chelating agent enters the aqueous phase, thus avoiding any adverse effects on subsequent reactions.
[0016] In existing technologies, the aqueous phase solution, due to its low polyphenylene ether (PPE) concentration, is difficult to directly recycle and reuse, and is generally treated as wastewater, resulting in resource waste and environmental harm. To fully utilize this aqueous phase solution and achieve better economic benefits, this invention proposes a method using a mixture of aromatic hydrocarbons and alkyl imidazoles as an extractant to effectively extract the aqueous phase solution separated during PPE production. The supernatant solution after extraction contains PPE oligomers and organic amines. In subsequent reactions, 2,6-dimethylphenol, cuprous salt, and chain extenders are added, and if necessary, additional organic amines are added. The reaction continues in the reactor, yielding a high-quality PPE product with significantly reduced oligomer content, a weight-average molecular weight of 40,000-60,000, a narrow molecular weight distribution (2.4-2.8), and good mechanical strength. This method of aqueous phase re-reaction in PPE production has shown stable operation and normal, unobstructed operation for six months, with no significant increase in filter pressure. This is a streamlined production process for polyphenylene ether (PPE) manufacturers. It simply involves changing the flow of the aqueous solution from the existing PPE production line, which originally went to the solvent recovery unit, to a re-reaction system comprising an alkali addition device 1, a mixing and stirring device 2, an extractor 3, a cooling device 4, and a reaction vessel 5. The reaction system is as follows: Figure 1 As shown. Among them, the mixing and stirring device 2 is equipped with a pH meter, which is used to regulate the amount and rate of alkali added to the alkali adding device 1.
[0017] Further, the alkaline solution mentioned in step (S1) is a 15-30 wt% aqueous solution of sodium hydroxide and / or potassium hydroxide, and the amount of alkaline solution added is to adjust the pH of the mixture obtained in step (S1) to 9-11. Under the action of the alkaline solution, most of the chelating agent will enter the aqueous phase and will not be extracted by the extractant. Another function of the alkaline solution is neutralization, which allows the amine to be extracted smoothly.
[0018] Further, in step (S2), the extractant is a mixture of aromatic hydrocarbon and alkyl imidazole ionic liquid in a mass ratio of 6-10:1, and the amount of extractant added is 1-1.5 times the mass of the mixture in step (S1). Preferably, the aromatic hydrocarbon is selected from at least one of benzene, toluene, and xylene; the imidazole ionic liquid is selected from at least one of 1-butyl-3-ethylimidazolium chloride, 1-butyl-3-ethylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1,3-dimethylimidazolium tetrafluoroborate. More preferably, the extractant is a mixture of toluene and 1-butyl-3-ethylimidazolium chloride in a mass ratio of 6-10:1. Using the above-mentioned compounded extractant, the extraction efficiency is optimal, the post-processing is simple, the yield of polyphenylene ether is high, and the quality is good.
[0019] The inventors unexpectedly discovered that adding a small amount of imidazole ionic liquid to the conventional good solvent aromatic hydrocarbons for polyphenylene ether (PPE) facilitates the extraction of PPE oligomers and ensures the complete extraction of mixed amines. Thus, in subsequent reaction stages, only the addition of cuprous salt is needed to continue the reaction. If the organic amine content in the system is insufficient, only a small amount of organic amine needs to be added; no further addition of organic amine is required, or only a small amount needs to be added. The organic amine acts as a catalyst during PPE production, forming a copper complex with the cuprous salt. The organic amine is selected from at least one of N,N-dimethyl-n-butylamine, N,N-di-n-butylamine, 1,3-dimethylbutylamine, dimethylethylenediamine, di-tert-butylethylenediamine, dimethylpropylenediamine, ethylbutanediamine, and trimethylpentanediamine.
[0020] Furthermore, in step (S3), the temperature of the cooling zone is 15-20°C; at this temperature, polyphenylene ether and oligomers, as well as organic amines, can be fully extracted into the toluene phase.
[0021] Furthermore, in step (S3), the lower liquid phase is treated as wastewater and sent to a distillation tower for further treatment.
[0022] Further, in step (S4), the chain extender is selected from C2-6 diols, specifically from at least one of 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol.
[0023] Furthermore, in the above preparation method, the relationship between the materials satisfies the following: the mass ratio of polyphenylene ether oligomer, 2,6-dimethylphenol, chain extender, and cuprous salt in the aqueous solution in step (S1) is 100:10-20:6-10:0.1-0.3. The amount of chelating agent added is 1.1-1.3 times the amount of cuprous salt.
[0024] Furthermore, in step (S4), a quaternary ammonium salt is added. The amount of quaternary ammonium salt added is 1-2 wt% of the polyphenylene ether oligomer in the aqueous solution in step (S1). The quaternary ammonium salt is selected from at least one of tetrabutylammonium bromide, methyltributylammonium chloride, methyltributylammonium bromide, methyltrioctylammonium bromide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltriethylammonium chloride, and benzyltriethylammonium bromide. Adding a small amount of quaternary ammonium salt can increase the catalytic efficiency and further improve the yield.
[0025] Further, in step (S4), the oxygen-containing gas is air or oxygen, and the amount of oxygen-containing gas introduced is 0.8-1.1 times the amount of 2,6-dimethylphenol added per hour, calculated based on oxygen content. Insufficient oxygen introduction will prevent the reaction from completing smoothly, resulting in low utilization of 2,6-dimethylphenol and a reduced yield. Excessive oxygen introduction may lead to side reactions or waste of oxygen.
[0026] In step (S4), the reaction temperature is 40-60℃ and the reaction time is 2-3h.
[0027] Step (S4), the post-processing after the reaction is well known in the art. Specifically, the reaction liquid is centrifuged, the water content of the oil phase is controlled to be <0.5%, and then it is concentrated in a vacuum flash evaporator until the solid content is above 60%. After cooling, it is poured into 6-10 times its volume of a poor solvent for polyphenylene ether to precipitate the precipitate. The precipitate is then filtered, washed, and dried to obtain the finished polyphenylene ether product. The poor solvent for polyphenylene ether is selected from methanol and acetone.
[0028] According to the above method of the present invention, the weight-average molecular weight of the obtained polyphenylene ether is between 30,000 and 45,000, and the molecular weight distribution is between 2.4 and 2.9, indicating good product quality. Attached Figure Description
[0029] Figure 1 This is a schematic diagram of the aqueous phase re-reaction system in the production of polyphenylene ether according to the present invention. Detailed Implementation
[0030] The aqueous solution containing polyphenylene ether oligomers used in the production process of polyphenylene ether in this embodiment of the invention is obtained through the following process: First, a certain amount of toluene is added as a good solvent for polyphenylene ether. In the presence of cuprous salt and organic amine, a small amount of 2,6-dimethylphenol is added as a PPE seed. Then, 2,6-dimethylphenol is added by weight under oxygen purging. The addition of 2,6-dimethylphenol is completed within 40 minutes. Subsequently, oxygen purging continues for reaction. After reacting for another 50 minutes, the oxygen supply is stopped, and the reaction is complete. Then, an aqueous solution of ethylenediaminetetraacetic acid is added, and the temperature is maintained between 50-75°C. Subsequently, the aqueous phase containing polyphenylene ether oligomers, cuprous salt, chelating agent, and other components is separated by solid-liquid separation to obtain the polyphenylene ether aqueous solution. After testing, the aqueous solution processed by this invention contains 9.2 wt% polyphenylene ether oligomers, 5.5 wt% mixed amines, 0.3 wt% cuprous salt, and 0.4 wt% ethylenediaminetetraacetic acid, wherein the weight average molecular weight of the polyphenylene ether oligomers is approximately 3000-5000.
[0031] The weight-average molecular weight was obtained using GPC gel permeation chromatography with polystyrene as a standard reference. The number-average molecular weight was obtained using the intrinsic viscosity method. The molecular weight distribution was calculated using Mw / Mn. For ease of calculation, the yield of the polyphenylene ether product of this invention was obtained using the following formula:
[0032] A represents the yield, m represents the mass of the finished polyphenylene ether product, m1 represents the mass of the polyphenylene ether oligomer in the aqueous solution, m2 represents the mass of the chain extender, and m3 represents the mass of 2,6-dimethylphenol.
[0033] Example 1
[0034] (S1) Add 20wt% NaOH aqueous solution to the aqueous phase solution separated during the production of polyphenylene ether using a metering pump, adjust the pH of the system to 10, and mix thoroughly.
[0035] (S2) Pump the mixture obtained in step (S1) into the extractor, and at the same time add toluene and 1-butyl-3-ethylimidazolium chloride in a mass ratio of 8:1 as the extractant, and mix them evenly; the mass ratio of the extractant to the aqueous solution in step (S1) is 1.3:1.
[0036] (S3) The mixture obtained in step (S2) enters the cooling zone and is cooled to 20°C. It is then allowed to stand and separate into layers. The upper liquid phase is sent to the reaction vessel, and the lower liquid phase is treated as wastewater and discharged after meeting the standards.
[0037] (S4) Add chain extender 1,4-butanediol, monomer 2,6-dimethylphenol, and cuprous chloride to the reactor; wherein the mass ratio of polyphenylene ether oligomer, 1,4-butanediol, 2,6-dimethylphenol, and cuprous chloride in the aqueous solution of step (S1) is 100:15:8:0.2; introduce oxygen at a rate equal to the amount of 2,6-dimethylphenol introduced per hour, react at 50°C for 2 hours, after the reaction is completed, add an aqueous solution of ethylenediaminetetraacetic acid (ethylenediaminetetraacetic acid is used at a rate of 1.2 times the amount of cuprous chloride), cool, let stand, separate into layers, the upper layer is polyphenylene ether solution, centrifuge at 4000 rpm for 10 minutes to make the water content <0.5%, enter a vacuum flash evaporator for concentration, concentrate to a solid content of 62%, cool, pour into 6 times anhydrous methanol, precipitate, filter the precipitate, wash three times with anhydrous methanol and anhydrous acetone respectively, and vacuum dry to obtain the polyphenylene ether product.
[0038] Example 2
[0039] The other conditions and operations are the same as in Example 1, except that the raw material ratio is: the mass ratio of polyphenylene ether oligomer, 1,4-butanediol, 2,6-dimethylphenol and cuprous chloride in the aqueous solution of step (S1) is 100:10:10:0.2.
[0040] Example 3
[0041] The other conditions and operations are the same as in Example 1, except that the raw material ratio is as follows: the mass ratio of polyphenylene ether oligomer, 1,4-butanediol, 2,6-dimethylphenol and cuprous chloride in the aqueous solution of step (S1) is 100:20:6:0.2.
[0042] Example 4
[0043] Other conditions and operations are the same as in Example 1, except that the raw material ratio is: the mass ratio of polyphenylene ether oligomer, 1,4-butanediol, 2,6-dimethylphenol and cuprous chloride in the aqueous solution of step (S1) is 100:8:8:0.2.
[0044] Example 5
[0045] The other conditions and operations are the same as in Example 1, except that the raw material ratio is as follows: the mass ratio of polyphenylene ether oligomer, 1,4-butanediol, 2,6-dimethylphenol and cuprous chloride in the aqueous solution of step (S1) is 100:25:8:0.2.
[0046] Example 6
[0047] The other conditions and operations are the same as in Example 1, except that in step (S4), 1 wt% of the mass of the polyphenylene ether oligomer in aqueous solution of benzyltrimethylammonium chloride is added to the reactor.
[0048] Example 7
[0049] The other conditions and operations are the same as in Example 1, except that in step (S4), 2 wt% of the mass of polyphenylene ether oligomer and methyl tributylammonium chloride are added to the reactor in an aqueous solution.
[0050] Comparative Example 1
[0051] The other conditions and operations are the same as in Example 1, except that in step (S2), the extractant is toluene.
[0052] Application examples
[0053] The polyphenylene ethers obtained in the above examples and comparative examples were tested, and the results are shown in Table 1 below:
[0054] Table 1
[0055]
[0056]
Claims
1. A method for aqueous phase re-reaction in the production of polyphenylene ether, comprising the following steps: (S1) The aqueous phase solution separated during the polyphenylene ether production process is added to the alkaline solution through a metering pump and mixed evenly; the aqueous phase solution contains 8-13 wt% polyphenylene ether oligomer, 4-7 wt% mixed amine, 0.1-0.4 wt% cuprous salt, and 0.2-0.6 wt% chelating agent. (S2) The mixture obtained in step (S1) is pumped into the extractor, and an extractant is added to the mixer and mixed evenly. The extractant is a mixture of aromatic hydrocarbon and imidazole ionic liquid in a mass ratio of 6-10:
1. The amount of extractant added is 1-1.5 times the mass of the mixture in step (S1). The aromatic hydrocarbon is selected from at least one of benzene, toluene, and xylene. The imidazole ionic liquid is selected from at least one of 1-butyl-3-ethylimidazolium chloride, 1-butyl-3-ethylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1,3-dimethylimidazolium tetrafluoroborate. (S3) The mixture obtained in step (S2) enters the cooling zone, is allowed to stand and separate into layers, the upper layer material goes to the reaction vessel, and the lower liquid phase is treated as wastewater. (S4) Add chain extender, 2,6-dimethylphenol, and cuprous salt to the reactor, and pass oxygen-containing gas to carry out the reaction. After the reaction is completed, add chelating agent aqueous solution, cool, stand, and separate into layers. The upper layer is a polyphenylene ether solution. After post-treatment, the polyphenylene ether product is obtained.
2. The method for aqueous phase re-reaction in the production of polyphenylene ether according to claim 1, characterized in that, The alkaline solution mentioned in step (S1) is a 15-30 wt% aqueous solution of sodium hydroxide and / or potassium hydroxide, and the amount of alkaline solution added is to adjust the pH of the mixture obtained in step (S1) to 9-11.
3. The method for aqueous phase re-reaction in the production of polyphenylene ether according to claim 1, characterized in that, The extractant is a mixture of toluene and 1-butyl-3-ethylimidazolium chloride in a mass ratio of 6-10:
1.
4. The method for aqueous phase re-reaction in the production of polyphenylene ether according to claim 1, characterized in that, In step (S3), the temperature of the cooling zone is 15-20℃.
5. The method for aqueous phase re-reaction in the production of polyphenylene ether according to claim 4, characterized in that, In step (S3), the lower liquid phase is treated as wastewater and sent to a distillation tower for further treatment.
6. The method for aqueous phase re-reaction in the production of polyphenylene ether according to claim 1, characterized in that, In step (S4), the chain extender is a C2-6 diol.
7. The method for aqueous phase re-reaction in the production of polyphenylene ether according to claim 6, characterized in that, The chain extender is selected from at least one of 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol.
8. The method for aqueous phase re-reaction in the production of polyphenylene ether according to claim 1, characterized in that, In the preparation method, the relationship between the materials satisfies the following: the mass ratio of polyphenylene ether oligomer, 2,6-dimethylphenol, chain extender and cuprous salt in the aqueous solution in step (S4) is 100:10-20:6-10:0.1-0.3; the amount of chelating agent added is 1.1-1.3 times the amount of cuprous salt.
9. The method for aqueous phase re-reaction in the production of polyphenylene ether according to claim 1, characterized in that, In step (S4), a quaternary ammonium salt is also added. The amount of quaternary ammonium salt added is 1-2 wt% of the amount of polyphenylene ether oligomer in the aqueous solution in step (S1). The quaternary ammonium salt is selected from at least one of tetrabutylammonium bromide, methyltributylammonium chloride, methyltributylammonium bromide, methyltrioctylammonium bromide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltriethylammonium chloride, and benzyltriethylammonium bromide.
10. The method for aqueous phase re-reaction in the production of polyphenylene ether according to claim 1, characterized in that, In step (S4), the oxygen-containing gas is air or oxygen, and the amount of oxygen-containing gas introduced is 0.8-1.1 times the amount of 2,6-dimethylphenol added per hour, calculated according to the oxygen meter. In step (S4), the reaction temperature is 40-60℃ and the reaction time is 2-3h.